The invention relates to cast shafts, particularly camshafts and other slender or small-diameter shafts, which are cast in one piece and which are provided with a central longitudinal channel cast therein.
Slender, cast shafts are required in large numbers in the form of camshafts for the construction of internal combustion engines. Through the disk cams, called cams, distributed over the length of the shaft, inlet and outlet valves are controlled directly or via a linkage, e.g. push rods and rocker arms. These camshafts which can rotate at half the engine speed are exposed to significantly changing bending and torsional loads. The vibrational behavior of such camshafts is consequently of great significance.
Steel camshafts are particularly used in large internal combustion engines, whereas preference is given to cast camshafts for vehicle engines.
The invention relates to cast iron, cast camshafts, as well as to other similar, slender cast shafts. These shafts advantageously have high damping characteristics and can be manufactured at relatively low cost. A further advantage of the cast shaft is that the central longitudinal channel, such as is provided in many camshafts, can also be provided during the casting operation. This central longitudinal channel serves to supply lubricating oil, e.g. for lubricating the cams and bearing points. For this purpose it is necessary to drill in the camshaft transverse channels branching off the longitudinal channel in order to permit the exit of lubricating oils at predetermined points distributed over the length of the camshaft as disclosed, for example, in U.S. Pat. No. 3,689,986. An additional machining operation is required for drilling these transverse channels and usually a special drilling machine must be employed. The time and mechanical expenditure required for this operation constitutes an important feature in the overall costs involved in the manufacture of the camshaft.